Selective activation of C–F and C–H bonds with iron complexes, the relevant mechanism study by DFT calculations and study on the chemical properties of hydrido iron complex?

Dalton Transactions Pub Date: 2012-11-20 DOI: 10.1039/C2DT31795H

Abstract

The reactions of (2,6-difluorophenyl)phenylmethanone (2,6-F2C6H3–C([double bond, length as m-dash]O)–C6H5) (1) and (2,6-difluorophenyl)phenylmethanimine (2,6-F2C6H3–C([double bond, length as m-dash]NH)–C6H5) (3) with Fe(PMe3)4 afforded different selective C–F/C–H bond activation products. The reaction of 1 with Fe(PMe3)4 gave rise to bis-chelate iron(II) complex [C6H5–C([double bond, length as m-dash]O)–3-FC6H3)Fe(PMe3)]2 (2) via C–F bond activation. The reaction of 3 with Fe(PMe3)4 delivered chelate hydrido iron(II) complex 2,6-F2C6H3–C([double bond, length as m-dash]NH)–C6H4)Fe(H)(PMe3)3 (4) through C–H bond activation. The DFT calculations show the detailed elementary steps of the mechanism of formation of hydrido complex 4 and indicate 4 is the kinetically preferred product. Complex 4 reacted with HCl, CH3Br and CH3I delivered the chelate iron halides (2,6-F2C6H3–C([double bond, length as m-dash]NH)–C6H4)Fe(PMe3)3X (X = Cl (5); Br (6); I (7)). A ligand (PMe3) replacement by CO of 4 was observed giving (2,6-F2C6H3–C([double bond, length as m-dash]NH)–C6H4)Fe(H)(CO)(PMe3)2 (8). The chelate ligand exchange occurred through the reaction of 4 with salicylaldehydes. The reaction of 4 with Me3SiC[triple bond, length as m-dash]CH afforded (2,6-F2C6H3–C([double bond, length as m-dash]N)–C6H5)Fe(C[triple bond, length as m-dash]C–SiMe3)(PMe3)3 (11). A reaction mechanism from 4 to 11 was discussed with the support of IR monitoring. The molecular structures of complexes 2, 4, 6, 7, 10 and 11 were determined by X-ray diffraction.

Graphical abstract: Selective activation of C–F and C–H bonds with iron complexes, the relevant mechanism study by DFT calculations and study on the chemical properties of hydrido iron complex
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